Tool for torsion bar repair

ABSTRACT

A method and tool assembly ( 10 ) for unloading and reloading spring energy from a torsion bar ( 11 ) in a torsion bar suspension system of a motor vehicle. The tool assembly ( 10 ) includes a generally C-shaped body ( 14 ) having a screw shaft ( 24 ) threaded through a boss ( 22 ) in a lower section ( 18 ) thereof. An anti-rotation stem ( 38 ) includes a knurled flat face ( 40 ) which increases versatility of the tool assembly ( 10 ) by enabling anti-slip operation with various vehicle types. A counter-torque tool perch ( 46 ) extends from the lower section ( 18 ) of the tool body ( 14 ) for applying a counter-rotational torque to the body ( 14 ) during use of the tool assembly ( 10 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/026,493 which was filed on Feb. 6, 2008, the entire disclosure ofwhich is hereby incorporated by reference and relied upon.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to a tool of the type used to service atorsion bar suspension system in a motor vehicle, and more particularlytoward an unloading tool used to remove and restore spring energy in atorsion bar suspension system.

Related Art

Some motor vehicle suspensions use a torsion bar as a weight bearingspring. In this arrangement, one end of a long, usually metal torsionbar is attached firmly to the vehicle chassis and its opposite end isattached to an unsprung suspension component such as a suspension arm,spindle, axle or the like. Vertical motion of the vehicle wheel causesthe torsion bar to twist which is resisted by the torsion bar's inherentspring resistance. The end of the torsion bar that is attached to thechassis is usually fitted with a crank-like or lever-like adjusting armthat is controlled by an adjusting bolt to accomplish height adjustmentsof the spring-weight portions of the vehicle. Over time, fatigue, wearand creep will necessitate periodic height adjustment of the torsion barsuspension system as part of routine vehicle maintenance. Likewise, achange in wheel size or the addition of a so-called “lift kit” may alsonecessitate adjustment of suspension height by manipulating theadjustment arm portion of the torsion bar suspension system. For thispurpose, the adjusting bolt is fitted between the adjusting arm and arigid hollow frame rail, in which the adjusting arm is stationed. Insidethis hollow frame rail, the adjusting area remains relatively sheltered.

In order to service the torsion bar suspension system, which may includereplacing the torsion bar or recalibrating the adjusting arm, it isusually necessary to relieve all of the stored spring energy in thetorsion bar and also remove the adjusting bolt. Relieving the storedspring energy in a controlled manner can be a difficult and somewhatdangerous operation, as the torsion bar stores a tremendous amount ofenergy and the adjusting bolt is held in compression between theadjusting arm and the frame rail. Therefore, an unloading tool isrequired to temporarily transfer spring energy away from the adjustingbolt so that it can be removed or disabled before carefully releasingall of the torsion spring energy.

Current unloader tools have been proposed and are variously configured.One common type of unloader tool resembles a C-clamp which is placedover the frame rail and its screw shaft turned into engagement with theadjusting arm. By advancing the screw shaft far enough, spring energy istransferred from the adjusting bolt to the unloader tool. Once theadjusting screw has been disabled, the unloader tool can be manipulatedto slowly release the stored spring energy. Other examples of prior artunloader tools may be configured differently, such as resembling a wheelor gear puller, but operate in the same general fashion.

A problem inherent with all of the prior art unloader tools resides intheir tendency to slip out of position during operation. Due to theextremely large amounts of energy stored in a torsion spring, a slippingunloader tool can cause injury or damage when the stored energy isreleased in an uncontrolled manner. Some attempts have been made toaddress the slippage problem. For example, in many General Motors trucksequipped with torsion bar suspension, a small pilot hole is formed inthe top of the frame rail, and a special unloader tool includes a smallstem adapted to register in the pilot hole. When this style of unloadertool is hung over the rail, the stem on the unloader tool seats in thepilot hole in the frame rail, thus helping to keep it in position duringthe unloading process. However, this stem prevents the GM-style unloadertool from being used to work on suspension systems which are notequipped with a hole in the frame rail. Therefore, this type of priorart unloader tool is not at all versatile and therefore it is notattractive to service operators that repair various makes and styles oftorsion suspension systems.

Furthermore, prior art unloader tools are susceptible to twisting out ofposition or into disadvantageous positions as the screw shaft istightened against the adjusting arm or as attempts are made to carefullyrelease the stored energy. As stated earlier, there is extremely largeamounts of energy stored in the torsion spring, and therefore largeamounts of force are required to displace the adjusting arm sufficientlyfar enough to disable and re-enable the adjusting bolt during thevarious phases of a service operation. This large force creates a highdegree of friction at the point of contact between the tip of the screwshaft and the adjusting arm. This friction can cause the unloader toolto undesirably twist or shift out of position, increasing the chancesfor the tool slipping out of place and causing injury or damage. Tocounteract this undesirable twisting, a service operator may be temptedto use a free hand to hold the unloader tool in position. However, thisincreases the chances for injury. It is, in fact, not desirable for anoperator's fingers to be placed on or near the unloader tool as a safetymeasure in the event the tool slips out of position. Again, because ofthe very large amounts of force and energy involved, substantial injurymay result if the tool slips out of position while an operator's fingersare in close vicinity.

Accordingly, there is a need in this field to provide an unloading tool,and an improved method for safely unloading and reloading torsion springsystems, which is versatile among all motor vehicle makes and types,which is convenient to use, which is easy to manufacture and distribute,and which reduces the risk of injury to an operator.

SUMMARY OF THE INVENTION

This invention contemplates a tool assembly for unloading and reloadingspring energy in a torsion bar suspension system for a motor vehicle.The tool assembly comprises a tool body having upper and lower sections.The body includes a threaded boss formed integrally with the lowersection. A screw shaft is threadably engaged in the boss and extendsbetween leading and trailing ends. The screw shaft includes an anvil atits leading end generally opposing the upper section of the body, andalso a wrench receiving portion at the trailing end of the screw shaft.A counter-torque tool perch extends from the lower section of the bodyfor applying a counter-rotational torque to the body during use of thetool assembly.

The counter-rotational tool perch feature of the subject invention isideally suited to receive a wrench or other such tool so that a serviceoperator working on a torsion bar suspension system can use the subjecttool assembly in a manner that is safer than prior art systems. In otherwords, the counter-torque tool perch allows the operator to apply acounter-rotational torque to the body of the tool while the screw shaftis manipulated to service a torsion bar suspension system.

According to another aspect of this invention, a tool assembly isprovided for removing and reinstating spring energy in a torsion barsuspension system of a motor vehicle. According to this aspect of theinvention, the tool assembly comprises a tool body having upper andlower sections, with the body including a threaded boss at its lowersection. A screw shaft is threadably engaged in the boss and extendsbetween leading and trailing ends. The screw shaft includes an anvil atits leading end generally opposing the upper section of the body, and awrench receiving portion at its trailing end. The body includes ananti-slip stem along its upper section. The anti-slip stem includes aknurled face configured to prevent slippage during use of the toolassembly. The anti-slip stem substantially enhances the versatility ofthe subject invention by enabling its use and applicability across awide variety of motor vehicle types and makes. Thus, motor vehiclesequipped with small pilot holes in a frame rail section adjacent anadjusting arm of the torsion suspension system will receive theanti-slip stem to prevent shifting of the tool out of position duringuse. However, motor vehicle types that do not include a pilot hole willbenefit from the knurled face of the anti-slip stem which providessecure, biting engagement during use of the tool.

According to yet another aspect of this invention, a method is providedfor removing an adjusting bolt from a torsion bar suspension system in amotor vehicle. The method comprises the steps of providing a torsion barsuspension system having a loaded torsion bar, an adjusting arm affixedto one end of the torsion bar and sheltered within a hollow frame rail.An adjusting member, typically in the form of a bolt, is operativelydisposed between the adjusting arm and the frame rail. An unloader toolis provided having a body with upper and lower sections. A screw shaftof the unloader tool is threaded through its lower section. The methodfurther includes the step of positioning the upper section of the toolbody over the frame rail and locating the screw shaft of the unloadertool against the adjusting arm. Spring energy is transferred away fromthe adjusting member to the unloader tool by turning the screw shaftrelative to the body so that the screw shaft pushes the adjusting armaway from the adjusting member. The method further includes the step ofapplying a counter torque to the body of the unloader toolsimultaneously with the step of transferring spring energy away from theadjusting member to the unloader tool. Thus, the method of thisinvention represents an advancement in service safety by enabling acounter-torque to be applied to the body of the unloader tool at thesame time the screw shaft is advanced against the adjusting arm. As aresult, a service technician is better able to keep hands a safedistance from the unloading tool, as well as better control the tool andachieve swifter, more efficient results.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is a perspective view of an unloader tool according to thesubject invention;

FIG. 2 is a front elevation view of the subject unloader tool;

FIG. 3 is a view of the unloader tool taken generally along lines 3-3 ofFIG. 2;

FIG. 4 is an enlarged view of the anti-rotation stem as taken alonglines 4-4 in FIG. 2;

FIG. 5 is a view as in FIG. 4, but showing an alternative knurl patternapplied to the face of the anti-rotation stem;

FIG. 6 is a cross-sectional view as taken generally along lines 6-6 ofFIG. 5;

FIG. 7 is a simplified cross-sectional view showing a fragmentaryportion of a frame rail in a motor vehicle together with an adjustingarm sheltered therein, an adjusting bolt, and the unloader tool of thesubject invention poised for operation;

FIG. 8 is a perspective view showing the subject unloader tool disposedfor service operation with auxiliary wrenches applied according to thepreferred method of this invention; and

FIG. 9 is a cross-sectional view taken generally along lines 9-9 in FIG.7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, an unloader toolassembly according to the subject invention is generally shown at 10.The tool assembly 10 is of the type for removing an adjusting member ina torsion bar 11 suspension system for a motor vehicle. The adjustingmember can be a cam, wedge, ratchet or other mechanical orelectromechanical device, but in the most common applications comprisesan adjusting bolt 12 as depicted in FIGS. 7 and 8. The adjusting bolt 12is threaded through a cross-nut 13. The tool assembly 10 includes a toolbody, generally indicated at 14, having an upper section 16, a lowersection 18, and a riser section 20 interconnecting the upper 16 andlower 18 sections. In cross-section, each of the sections 16, 18, 20 areshown having a generally T-shaped configuration designed for maximumrigidity. Preferably, these sections 16-20 are arranged end-to-end intoa generally C-shaped configuration similar in some respects to theubiquitous C-clamp known from the woodworking and metalworking arts.

The lower section 18 of the tool body 14 includes an integral boss 22having, in the preferred embodiment, a generally cylindrical appearance.The boss 22 is internally threaded along a longitudinally extending axisA which may be skewed slightly relative to the riser section 20. In thepreferred example of this invention, the longitudinal axis A is cantedapproximately 5° relative to the inner surface of the riser section 20.However, this skewed configuration of the longitudinal axis A relativeto the riser section 20 is subject to alteration depending upon theintended application and other design factors.

A screw shaft 24 is threadably engaged in the boss 22 as shown in theFigures. The screw shaft 24 has a leading end and a trailing end. Ananvil, generally indicated at 26, is formed at the leading end of thescrew shaft 24 in an orientation that generally opposes the uppersection 16 of the tool body 14. A wrench receiving portion 28 is locatedat the trailing end of the screw shaft 24. Preferably, the wrenchreceiving portion 28 comprises a hex fitting, a square end fitting, orother feature having opposed flat faces so that a common wrench 30, likethat shown in FIG. 8, can apply a forceful twisting motion to the screwshaft 24. The anvil 26 at the leading end of the screw shaft 24 isperhaps best shown in FIGS. 1, 2 and 9 comprising a generallycylindrical trunk 32 capped by a hemispherical tip 34. The trunk 32 hasa diameter that is substantially smaller than the major diameter of thescrew shaft 24. Many adjusting arms 36, like those shown in FIGS. 7-9,are fitted with a small dimple or indentation adapted to receive theanvil 26 and help retain the leading end of the screw shaft 24 inposition against the adjusting arm 36 as it is raised and lowered toload and unload spring energy from the torsion bar 11 in a controlledmanner. Preferably, the anvil 26 is hardened in an appropriatemetallurgical process to resist wear.

The upper section 16 of the tool body 14 is roughened to resistslippage. In one embodiment, an anti-slip stem, generally indicated at38, protrudes from the inside surface of the upper section 16. Theanti-slip stem 38 either directly or approximately opposes the anvil 26of the screw shaft 24. In other words, the longitudinal axis A which iscommon with the screw shaft 24 preferably intersects the anti-slip stem38 so that pressure applied by contact between the anvil 26 and theadjusting arm 36 lies in a vector passing through the anti-slip stem 38.The anti-slip stem 38 includes a flat knurled face 40 configured toprevent slippage during use of the tool assembly 10. The face 40preferably lies in a plane normal to the longitudinal axis A. Theknurled face 40 is perhaps best shown in FIG. 4 comprising acriss-crossing pattern of hardened ridges. These ridges will bite intothe surface of a frame rail 42 as shown in FIGS. 7-9. FIGS. 5 and 6depict an alternative configuration for the knurled face 40′ wherein theknurling includes a plurality of concentrically oriented ridges. Thoseof skill will envision other possible configurations for the knurledface 40, 40′ which may be effective to achieve similar functionality;

Preferably the anti-slip stem 38 is provided with a tapering sidewall 44truncated by the generally flat knurled face 40. In other words, whilethe knurled face 40, 40′ is roughened by the criss-crossing, concentricridges, or the like, it is nevertheless flat in that it truncates thetapering sidewall 44, which in the preferred embodiment, achieves agenerally frustoconical shape. The size of the sidewall 44, 44′ isdimensioned to fit in a small pilot hole formed in the frame rail 42common in some motor vehicle makes. Thus, in vehicles equipped with apilot hole in the frame rail 42, which may include trucks manufacturedby General Motors Corporation, the anti-slip stem 38 will register inthe pilot hole and thereby help prevent the tool assembly 10 fromslipping out of position during use. However, in motor vehicles notequipped with a pilot hole in the frame rail 42, the knurled face 40will bite into the frame rail 42, thereby providing adequate purchaseand resistance to tool 10′ slippage during use.

The tool body 14 may include a roughened surface 41 on the insidesurface of the upper section 16. This roughened surface 41 may either beapplied as a supplement to the anti-slip stem 38 as shown, or used inlieu of the anti-slip stem 38. The roughened surface 41 is shown as acut pattern of crossing grooves but could alternatively be a series ofridges, sprayed thermal coating, or other of the various knowntechniques.

The tool body 14 may include a counter-torque tool perch, generallyindicated at 46, extending from its lower section 18 and laterallyoffset from the boss 22. The tool perch 46 includes at least two, butpreferably six, flat faces 48 arranged to receive a standard sized openwrenching device 50 as shown in FIG. 8. Thus, in the preferredembodiment of this invention, the tool perch 46 has a generallyhexagonal cross-section and may be oriented generally parallel to thelongitudinal axis A. An imaginary axis extending along the length of thetool perch 46 would, in the preferred embodiment, be parallel to thelongitudinal axis A. This is perhaps best illustrated in FIG. 2. Thetool perch 46 is particularly effective in applying a counter-rotationaltorque to the tool body 14 during use of the assembly 10. The tool perch46 increases operator safety by providing a convenient, tool receivinglocation at which to counteract torsional forces which might otherwisebe applied to the tool assembly 10 by the primary wrench 30 turning thescrew shaft 24. By laterally offsetting all of the faces 48 of the toolperch 46 away from the boss 22, clearance for a box-end or socket-typewrench 50 is provided, along with additional operator control isprovided over the tool assembly 10. In other words, additional momentscan be created by the two wrenches 30, 50 when applied to the toolassembly 10 which, in the hands of a skilled service technician, willpermit a highly advanced ability to finesse the tool assembly 10 duringdifficult and hard-to-reach service procedures. Furthermore, the spacebetween the tool perch 46 and boss 22 enables the secondary wrench 50 tobe of the box-end type (shown) or socket-type, in addition to open-endtype wrenches. Box-end and socket-type wrenches are preferred, however,because they are less likely to slip off the tool perch 46 during use,thereby enhancing user safety. Along these same lines, another inherentbenefit is gained by laterally offsetting the tool perch 46. Thestandard box-end wrench 50 has a handle that is canted about 15° fromthe encircling socket portion. This canted handle provides greater handclearance below the frame rail 42. Thus, without sacrificing toolpurchase, the offset tool perch 46 further contributes to user safety.

Referring now to FIGS. 7-9, a method for disabling an adjusting bolt 12from a torsion bar suspension system in a motor vehicle will bedescribed in greater detail. The tool assembly 10 is positioned over ahollow frame rail 42 open along its bottom as shown, so that theanti-slip stem 38 either engages a pilot hole formed in the top of theframe rail 42 (some models) or finds purchase against a suitablesurface. The screw shaft 24 is then tightened by turning a wrench 30engaged with the wrench receiving portion 28 until the anvil 26 seatsinto the small dimple or pocket formed in the underside of the adjustingarm 36. A counter-rotational torque is simultaneously applied by asecondary, preferably box-end or socket-type wrench 50 fitted to thetool perch 46. Continued tightening of the screw shaft 26 will cause theadjusting arm 36 to push away from the adjusting bolt 12, therebytransferring all of the stress and compression forces from the storedspring energy into the tool assembly 10. This effectively un-stressesthe adjusting bolt 12 and allows it to be removed or disabled. With theadjusting bolt 12 disabled, its associated cross-nut 13 can be removedfrom the frame rail 42, thus unblocking the channel-like interior of theframe rail 42 so that the adjusting arm 36 is free to swing a wide arc.The screw shaft 24 is then retracted, allowing the torsion barsuspension system to unload its stored energy in a safe, controlledmanner. This causes the tip of the adjusting arm 36 to rotate out of thehollow frame rail 42. The tool assembly 10 is then removed and anyrequired service operation is performed by a qualified technician.

After servicing the torsion bar suspension system, the tool assembly 10is reattached to the frame rail 42 and the screw shaft 24 tightenedagainst the torsion bar adjusting arm 36 to reload or restore energyback into the torsion bar suspension system. With spring energy in thesuspension system reloaded, the cross-nut 13 and adjusting bolt 12 arereinstalled and poised to return to active service in engagement withthe adjusting arm 36. At this stage, the service technician carefullybacks out the screw shaft 24, allowing spring energy to be transferredback to the adjusting bolt 12 and cross-nut 13. When this transfer ofload is complete, the tool assembly 10 is removed.

A particular advantage of the subject method allows a service technicianto apply a counter-torque to the tool body 14 with a box-end orsocket-type wrench 50 simultaneously with the step of transferringstress from the adjusting bolt 12 to the tool assembly 10 so as toprevent the tool assembly 10 from slipping out of position. This is donein a manner which improves safety for the service technician and enablesa greater degree of control by centering the counter-torque at alocation which is laterally offset from the screw shaft 24.

The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and fallwithin the scope of the invention. Accordingly the scope of legalprotection afforded this invention can only be determined by studyingthe following claims.

What is claimed is:
 1. A tool assembly comprising: a tool body havingupper and lower sections, said body including a threaded boss formedintegrally with said lower section; a screw shaft threadably engaged insaid boss and extending between leading and trailing ends, said screwshaft including an anvil at said leading end generally opposing saidupper section of said body and a wrench receiving portion at saidtrailing end; and a counter-torque tool perch extending from said lowersection of said body for applying a counter-rotational torque to saidbody during use of said tool assembly.
 2. The tool assembly of claim 1wherein said counter-torque tool perch is laterally offset from saidboss and includes at least two flat faces.
 3. The tool assembly of claim1 wherein said counter-torque tool perch has a generally hexagonalcross-section spaced apart from said boss.
 4. The tool assembly of claim1 wherein said body has a riser section extending between said upper andlower sections thereof, with said upper, lower and riser sectionsforming a generally C-shaped configuration.
 5. The tool assembly ofclaim 1 wherein said screw shaft has a major diameter along its length,and said anvil comprises a generally cylindrical trunk having a diameterless than said major diameter and a hemispherical tip adjoining saidtrunk.
 6. The tool assembly of claim 1 wherein said body includes aroughened surface along said upper section thereof.